1. Field of the Invention
The present embodiment relates to a light-emitting device and a lighting system.
2. Description of the Related Art
A light-emitting diode (LED) is a device which converts electric signals into light using characteristics of compound semiconductors. LEDs are now being applied to devices such as home appliances, remote controls, electronic boards, displays, a variety of automatic appliances and the like and their application range continues to expand.
As the application range of LEDs expands, brightness required for lights in daily use and lights for structural signals increases. Accordingly, it is important to increase luminous efficacy of LEDs. However, a semiconductor layer such as GaN grown on a hetero-substrate such as a sapphire substrate has crystal defects due to lattice mismatch between the semiconductor layer and the hetero-substrate. These defects may have a negative effect on reliability of the light-emitting device and absorb light, thus reducing brightness thereof.